1. Field of the Invention
This invention relates in general to electrically driven submersible pumps, and in particular to a means for sensing pressure and temperature at the pump and providing a surface readout concurrently.
2. Description of the Prior Art
The submersible pump installations concerned herein include a large electric motor located in the well. the electric motor receives three-phase power over a power cable from the surface. The electric motor drives a centrifugal pump to pump well fluid to the surface.
It is desirable to be continuously aware at the surface of the downhole operating conditions of the pump. This includes knowledge of the pressure of the lubricant in the motor, which is substantially the same as the well fluid pressure, and also the temperature. It would also be useful to have a surface readout of other environmental parameters, such as water content of the motor lubricating oil.
U.S. Pat. No. 3,340,500, Sept. 5, 1967, Boyd, et al, shows a means for measuring the pressure in a submersible pump system. U.S. Pat. No. 4,178,579, Dec. 11, 1979, McGibbeny, et al., shows means for measuring both pressure and temperature by using steering diodes and a relay. Both of these patents show devices that superimpose a DC level on the AC power conductors, with the changes in the DC level being proportional to the physical parameters sensed. There are other patents that show this telemetry means as well. No prior art known to applicants shows means for measuring more than two physical parameters, or means for sensing the parameters other than by superimposing a DC level on the AC power conductors.